Personnal reflexions around Oracle and my applications

New Exadata mode for DBMS_STATS.GATHER_SYSTEM_STATS

There is a new configuration in DBMS_STATS that can help Oracle to understand that it is working on an Exadata.

Most of the time the FULL TABLE SCAN is more performant than an INDEX SCAN on Exadata systems (i say most of the time, so i mean you have to test by yourself). The problem of this is with default system stats.
With the default system stats does not know that a FTS may be less expensive than accessing an index.

To help Oracle to know it is working on a EXADATA system there is a new GATHER_SYSTEM_STATS mode exclusively for EXADATA.

To enable this new mode you have to execute the following command

exec dbms_stats.gather_system_stats('EXADATA');

This new mode is available from the 11.2.0.2.18 or 11.2.0.3.8 (nore information on Metalink note Oracle Sun Database Machine Setup/Configuration Best Practices [ID 1274318.1])